The present invention relates to a packing box used for lead terminal type semiconductor devices, including insulated gate type semiconductor devices such as MOSFETs and IGBTs.
The gates of insulated gate semiconductor devices or products such as a MOSFETs or IGBTs may break down if electrostatic voltage is applied accidentally between the terminals. Therefore, electrostatic voltage must be prevented when such semiconductor products are shipped or stored.
The semiconductor products, structure of conventional packing boxes, and conventional packing procedure as stated above are explained with reference to FIGS. 4 and 5. FIG. 4 shows a shape or configuration of a single in-line type lead terminal semiconductor device, wherein reference numeral 1 represents a resin package incorporating therein the insulated gate semiconductor elements such as MOSFETs and IGBTs alone or together with other electronic elements, and reference numeral 2 represents lead terminals projecting from the package 1 and arranged linearly.
In order to pack such semiconductor products before shipment, a corrugated fiberboard packing box 3 as shown in FIG. 5 has been prepared. The packing box 3 comprises a box body 3a, inner partitions 3b, and an upper cover 3c. When semiconductor products 4 are packed in the packing box 3, the products 4 are put in conductive bags 5, which shield the products electrostatically. The products are then placed in the box 3 so that the lead terminals 2, which are not mechanically strong, orient upwardly. The cover 3c is then placed on the box body 3a. Instead of the conductive bag 5, a piece of metal may be attached to the lead terminals 2 of each semiconductor product for short-circuitting to thereby prevent the product from breakdown due to electrostatic voltage.
The above conventional packing method is, however, not very efficient because each semiconductor product 4 must be put in a conductive bag, or some other method must be applied to prevent the product from breakdown due to electrostatic voltage before the products are packed in the packing box 3. This method is also troublesome when the packing box 3 is opened at the destination to take out the semiconductor products 4, because each product 4 must be picked up from a portion situated between the inner partitions 3b of the box body 3a, and the bag 5 must then be removed. Furthermore, the semiconductor products may shake and collide with the cover or side wall of the box 3 as a result of shocks or vibrations that may occur during transportation, to thereby cause the lead terminals 2 to be damaged.
In view of the above problems, the present invention has been made, and it is objects of the invention to provide a packing box for solving the problems that often occur with the lead terminal type semiconductor products, and for allowing the products in the box to be securely held in place, for enabling simple packing and taking out the products as well as for preventing the product from breakdown due to electrostatic voltage.